Electron ray scanning device



April 19, 1949. P. M. G. TOULON 2,467,786

ELECTRON RAY SCANNING DEVICE Filed Nov. 2, 1956 4 INVENTOR PIERREMARIEGABRIELTOULON BY I ATTORNEY Patented Apr. 19, 1949 2,467,786 1ELECTRON BAY SCANNING DEVICE Pierre Marie Gabriel Toulon, Paris, France,as-

signor to Societe Generale de Machines et Brevets, Geneva, Switzerland,a corporation of Lichtenstein Application November 2, 1936, Serial No.108,762 In France November 6, 1935 Section 3 Public Law .690, August 8,1946 Patent expires November 6, 1955 8 Claims.

The. inv ntion relates, to television apparatus nd more. pa icularly toscann n proces for same- Th p ob m of scan ing a surfa becomes more diiicult as the number of eXplored poin s Per second creases. Wit the s anin tt. e. rate of; 59 ict re fir undredr ine frames he: i ht beam sould. be dis laced by the optical qr mec ani al systems a v y hi h pe sa d h :lummous lux emitted or received is very small.

T e cbiect Of th resent in ention is to pr ui de a new scanning devicethat has the advanage: oi b in an ntire y el t c l d v hereby' greateeeds a be b aine t be on s tc that, class of scanners where the. imageis entirely projected on a photoelectric surface.

according to the invention the surface setup s btain d; p i t by oi y ntrposina be we n h s ac a d a o e i ele trode. a s u-itably energizedscanning device which only allows, the emitted electrons to pass at asingle p, nt. This, energizing variable so that the Pbint is eeuiinual'lsh fted- The process can be applied not only to the transmitters(photoelectric surface) but also to the receivers (for example anelectromemitting surtaceor a slow-discharge tube).

In the following description and for a better understanding of the.apparatus the process has been represented as applied to aphoto-electric cell of rectilinear operating characteristics as foreganrhle. is used tor scanning a horizontal line of a. movingpicturei'llm.

Figure, l showspartly in section, the general principle. of thearrangement of the electrodes the photo-cell for performing the scanningprocess; and Figures 2 and 3- are diagrams shoW- the. potentials ofvarious points on the various grids as function of time and illustratingtheir operation It, should be understood that these figures are merelygiven as illustrating an example of the invention.

In Figured, l is av cathode emitting electrons under the action of lightrays supplied through lenszwhich projects the televised image. on saidcathode.

According to, the invention two grids. are interposed betweencathode. Iand anode 3, one being shown. at 4-15 and the-other at 6'l.

The emitted electrons can only reach the collecting anode 3 if thepotential of these two grids located in the path of travel between anodeand cathode is positive. Should either one of the grids be brought to anegative potential the electrons will no. longer be able to travel alonga straight line and they will fall back onto the Qdlrhpdc,

Ifhe grids are made of resistance wire so, that the; different meshes ofwhich they consist. are

brought to different potentials; it may be for ex: a ple a si ant ire.arr n ed igzag fashio The ends of grid 4-4 are connected to a battery 8allowing of a weal; currentfiowing through this resistance. The effectof this current is to bring e a ous and c -Sh to a se ies f pot n ials.showing gradual increase from one to another. Under these conditionsintermediate points such as 9. it, I! are impressed with difierent po-.tentials ranging in close vicinity to one another between the potentialsof the terminal parts 4 and 5. Grid ii? is connected likewise to abattery l2 so that the meshes i3, id, 55 are brought to a series ofslightly difiering potentials comprised between those of points 6 and l.The tension ape, plied to the whole of grid l..5 on the one hand.

and to grid E-l on the other hand is modulatfid, that is to say thepotential, value of all thmeshes on either grid varies as a functionOf.- time.

Under these conditions there never but one point on cathode l facingwhich the meshes of the two grids are simultaneously at potential zero;and through this point only are electrons given off by thephoto-electric process able to escape and reach anode 3. v

The principle of the scanning process can be grasped by consideringFigure 2. At l6, H, the tension of different points on grid 45 at agiven moment has been illustrated (tensions being shown as ordinates,and lengths associated with different points in the grid being carriedon the figure as abscissae) whilst at it, I8 is represented the tensionof different points of electrode [i.'! at the same instant. If thepotential at middle? point on these two grids is zero at the momentconsidered, only electrons given off by the mid dle part of the cathodewill reach the anode.

Modulation of grid li-5 with regard to grid 6l results in a slidingmovement being impart? ed to curve I 8l9 to the eiiect of bringing itfor example to l8, l9 (Fig. 3), Whilstline 45, i1; isshiftedto l6, l1.

The point at which these two lines intersect is thus shifted along theline of travel 24} owing to the potential variation between the twogrids. Thus it is possible to vary the fractional electronic image onthe cathode which in turn produces electrons which are collected by theanode, and thus the scanning process is performed. Source 2i suppliesthe alternate tension required for this scanning operation. Usually thescanning is made to proceed in the form of a saw tooth wave by means ofa. thyratron relaxator, i. e. a tube filled with gas under reducedpressure which pe riodically, causes the sudden discharge f con.-denser, whilst on the contrary the charging; of the latter proceedsslowly through a high resistance. By using polarisation sources 2! and22, suitable adjustment relatively to the cathode of the anode tensionon the one hand, and of two ids on the other hand can be obtained. Thissecond adjustment results in the upward displacement of straight line 20in Figures 2 and 3. This adjustment allows the cell to be put into themost favorable operating conditions.

The above example relates to a linear cell intended to transmit animatedfilms with a continuous movement. It is obvious that the same processcan be applied to surface cells. In the latter case one may either givea special shape and a particular arrangement to two abovementioned gridsor preferably insert a second structure of two grids in the path oftravel of the electrons. Two relaxation tubes will be used, oneenergizing a grid structure so as to provide a one-way scanning (linescanning) the other energizing the other structure of a much lowerfrequency (picture frequency).

This process can be applied to the receiving where it can be used tocause the illumination of a low pressure gas tube with emitting cathode.The electrons which passed beyond the set of the two grids now beingcapable of causing v the gas to become ionized or the emission of asecondary electron or any other optical phenomena.

Although only a single particular case has been represented of the newscanning process it is obvious that the new method of control by meansof two or more grids set at a suitably distributed potential andsuitably modulated can be made to ensure line 2 or pictorial scanningaccording to a predetermined law as well in the transmitter as in thereceiver of a television apparatus.

I claim:

1. In a television system, an apparatus for sequential scanning of theelemental areas of an image, including in combination anelectronemitting electrode, means for projecting light rays onto saidelectrode, grids interposed in the path of the electrons emitted by saidelectrode, a source of scanning potential, and means for impressing uponsaid grids oppositely phased modulating potentials from said source ofscanning potential.

2. In a television system, an extensive photo-sensitive electrode, apair of grid structures substantially co-extensive with said electrode,and means for impressing upon said grid structures uniformly distributeddirect current potential gradients and oppositely phased modulatingpotentials for establishing a point of zero potential at a single pointof said electrode, said point of zero potential being movable relativelyto said electrode in a scanning movement in response to said modulatingpotentials.

3. In a television system, a photo-sensitive linearly extensiveelectrode, including, a plurality of grid structures of resistance wire,said structures being co-extensive with said linearly extensiveelectrode, plural sources of direct current potential, said gridstructures being shunted by said sources in such manner as to produceuniformly distributed potential gradients therealong, and means forimpressing modulating potentials upon said grid structures,respectively, in such manner that a point of zero potential is producedat a single point upon said electrode, said point of zero potentialbeing movable along said electrode in a scanning movement in response tosaid modulating potentials.

4. In a television system, an apparatus for 4 sequential scanning of theelemental areas of an image, including, in combination, an extensivephoto-sensitive cathode for providing at different points of the surfacethereof electron emission of diiierent intensity, an anode forcollecting said electrons, a grid structure interposed between saidcathode and said anode for controlling the flow of electrons from saiddifferent points to said anode in succession, means for impressingdirect current potential gradients'on said grid structures, and meansfor impressing modulating potentials of mutually opposite phases uponsaid grid structures.

5. In a television system, an apparatus for sequential scanning of theelemental areas of an extensive image, including in combination, anextensive photosensitive cathode for producing electron emission locallyvariable thereon, in response to said image, an anode for collectingsaid electrons, grid structures interposed between said cathode and saidanode, and means for impressing constant direct current potentialgradients and varying modulating potentials upon said grid structures,respectively, for controlling electron flow from successive areaportions of said extensive cathode in time succession.

6. In a television system, an apparatus for sequential scanning of theelemental areas of an image, including in combination, an electronemitting photo-sensitive extensive electrode, means for projecting lightrays on a plurality of elemental areas of said electrode, a plurality ofgrids interposed in cascade in the path of electrons emitted by saidelemental areas of said electrode, a source of scanning potential, and

means for impressing upon said grids modulating potentials from saidsource of scanning potential for effecting electron flow from successiveones of said elemental areas in time succession.

7. In a television system, an apparatus for sequential scanning of theelemental areas of an image, including, an extensive photo-electronemitting electrode, means for impressing discrete elemental areas ofsaid image on discrete elemental areas of said electrode for producingalong all the surface of said electrode photoelectrons locally variablein intensity, a pair of grid structures co-extensive with saidelectrode, means for impressing upon said grid structures uniformlydistributed direct current potential gradients, and means for impressingupon said grid structures, respectively, oppositely phased modulatingpotentials.

8. In a television system, an apparatus for rectilinear sequentialscanning of the elemental areas of an image, including a rectilinearphotosensitive electron emitting electrode producing along all itslength electrons locally variable in intensity, a pair of gridstructures co-extensive with said electrodes, means for impressing uponsaid grid structures uniformly distributed direct current potentialgradients, and means for impressing on said grid structures,respectively, oppositely phased modulating potentials.

PIERRE MARIE GABRIEL TOULON.

REFEREBMJES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

